Fenestrated bone wrap graft

ABSTRACT

The present invention relates to a fenestrated bone wrap graft and a method of preparing cortical bone in thin sheets then fully demineralizing it to give it formed flexibility and then creating fenestrations in the cortical bone in a fashion similar to, but not identical to, skin grafts.

RELATED APPLICATIONS

This application is a continuation in part of co-pending U.S.application Ser. No. 14/556,492 entitled “Fenestrated Bone Graft” filedon Dec. 1, 2014.

TECHNICAL FIELD

The present invention relates to a fenestrated bone wrap graft and amethod of preparing cortical bone in thin sheets then fullydemineralizing it to give it formed flexibility and then creatingfenestrations in the cortical bone in a fashion similar to, but notidentical to, skin grafts.

BACKGROUND OF THE INVENTION

A bone graft is a surgical procedure used to fix problems associatedwith bones or joints. Bone grafting or transplanting of bone tissue isbeneficial in fixing bones after trauma, degenerative damage, problemjoints, or growing bone around implanted devices, such as total kneereplacement or spinal implants. The bone used in a bone graft can comefrom the patient, from a donor, or could be entirely manmade. Onceaccepted by the patient, the bone graft provides a framework where new,living bone can grow. The two most common types of bone grafts areallograft: this graft uses bone from a deceased donor or a cadaver thathas been cleaned and stored in a tissue bank and autograft: graft madefrom a bone inside a patient's body, such as the ribs or hips. The typeof graft used depends on the type of injury the surgeon will berepairing. Allografts are commonly used in hip, knee, or long bone (armsor legs) reconstruction. The advantages are that (a) there's noadditional surgery needed to acquire the bone, and (b) it lowers therisk of infection since additional incisions or surgery on the recipientwill not be required. Bone grafting is done for numerous reasons,including injury and disease. There are four main reasons bone graftsare used: fractures, a bone graft may be used in the case of multiple orcomplex fractures or those that do not heal well after an initialtreatment; fusion, most often done in the spine, fusion helps two bonesheal together across a diseased joint; regeneration, used for bone lostto disease, infection, or injury, this can involve using small amountsin bone cavities or large sections of bones; and implanted devices, agraft can be used to help bone heal around surgically implanted devices,like joint replacements, plates, or screws.

All surgical procedures involve risks of bleeding, infection, andreactions to anesthesia. Bone grafts carry these and other risks,including: pain, nerve injury, rejection of the bone graft andinflammation. The surgeon typically will make an incision in the skinabove where the graft is needed. He or she will then shape the donatedbone to fit the area. The graft will be held in place using variouspins, plates, or screws.

The present invention provides a new and improved type of bone graft anda method of manufacturing the graft to facilitate improved implantationtechniques.

SUMMARY OF THE INVENTION

The present invention relates to a fenestrated bone wrap graft and amethod of preparing cortical bone in thin sheets milled, ground orplaned to a very thin thickness (t) less than 1 mm then fullydemineralizing it to give it formed flexibility of a wrap or drape andthen creating fenestrations in the cortical bone in a fashion similar tobut not identical to skin grafts.

The advantage of this new bone wrap allograft is it provides a uniqueway to develop ingrowth through the fenestrations. The sheets can be cutup to 30 cm so they can be used for lateral lumbar fusions or evenmultiple fusions in the thoracic and lumbosacral spine. The graft beingso flexible it can also be folded or rolled, made into a pledget or plugas a construct that can be used inside of a spinal implant or can bedraped and folded over an implant to create an outer covering offlexible fenestrated bone. The flexibility also allows for the abilityto create different shapes such as a tube or a basket that can containeither allogeneric or autogeneric bone graft material with or withoutstem cells. The fenestrated bone wrap graft is relatively inexpensiveand easily scaled. The fenestrated bone graft is a device in which thereare created fenestrations which allow for the use bone sutures, suturematerial made from the same bone that can be used to weave the openingsin the fenestrated graft to create a variety of shapes like a cylinder,a basket, a wedge or a roll.

Preferably, a fenestrated cortical graft has an allograft bonestructure. The allograft bone structure has an exterior or outer surfaceand an interior or inner surface. The structure is fenestrated with aplurality of pores or openings extending through from the exterior orouter surface to the interior or inner surface to form open passages.The allograft bone structure can be formed as a very thin flat sheet.Alternatively, the allograft can be formed as a very thin walled tubularor cylindrical shaped graft. The allograft bone structure is preferablymade highly pliable. The pliable allograft bone structure is conformableto flex and wrap about the exterior surface of any 3-dimensionalstructure such as that of a damaged bone or implant device to provide afenestrated cortical bone wrap graft.

DEFINITIONS

As used herein and in the claims:

“BMA” refers to Bone Marrow Aspiration, a technique used to obtain theblood-forming portion (marrow) of the inner core of bone for examinationin the laboratory or for transplantation.

“Costal cartilage” refers to the cartilages that connect the sternum andthe ends of the ribs; its elasticity allows the chest to move inrespiration.

Demineralized bone matrix (DBM) is an osteoconductive and osteoinductivecommercial biomaterial and approved medical device used in bone defectswith a long track record of clinical use in diverse forms. True to itsname and as an acid-extracted organic matrix from human bone sources,DBM retains much of the proteinaceous components native to bone, withsmall amounts of calcium-based solids, inorganic phosphates and sometrace cell debris. Many of DBM's proteinaceous components (e.g., growthfactors) are known to be potent osteogenic agents. Commercially sourcedas putty, paste, sheets and flexible pieces, DBM provides a degradablematrix facilitating endogenous release of these compounds to the bonewound sites where it is surgically placed to fill bone defects, inducingnew bone formation and accelerating healing. Given DBM's long clinicaltrack record and commercial accessibility in standard forms and sources,opportunities to further develop and validate DBM as a versatile bonebiomaterial in orthopedic repair and regenerative medicine contexts areattractive.

The term “Fenestration” means openings in the walls of a structure.

“Pledget” means a compress or small flat mass usually of gauze orabsorbent cotton that is laid over a wound or into a cavity to applymedication, exclude air, retain dressings, or absorb the matterdischarged.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by way of example and with reference tothe accompanying drawings in which:

FIG. 1 shows 15-20 cm cortical demineralized graft with fenestrations,Freeze dried. Clinical usage for long segment fusion, segmental defectsas a wraparound intramedullary implant.

FIG. 2 shows Rib with fenestrations. Clinical indications, cranio andmaxillofacial surgery, spinal cage filler (can add micronized bone, dBM,MIAMI cells) to intact center.

FIG. 3 shows Demineralized rib; higher power magnification demonstratingfenestrations and cortical architecture.

FIG. 4 shows a fenestrated graft strip formed into a basket shape.

FIG. 5 shows a fenestrated graft strip formed into a basket held by asurgeon.

FIG. 6 shows a fenestrated graft strip formed as a pouch or pillowstuffed with a biologic material or stuffing to promote new bone growth.

FIG. 7 shows the bone wrap of the present invention formed as a verythin sheet of material made from cortical bone.

FIG. 7A is an enlarged view taken from FIG. 7 showing the fenestrations.

FIG. 8 is an implant device shown wrapped in the bone wrap of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIGS. 2 and 3, the original concept of fenestratingdemineralized cortical bone was developed in the rib 100 and the rib 100was an ideal graft because it can essentially be demineralized andcreates a large wide flat surface. After removal of the minimalcancellous center, the rib 100 is passed through a press with cutting orpunch blades that create fenestrations or openings 12 bounded byinterconnected bone struts 14 that gave the fenestrated bone graft 10 aporosity as well as stretchability and flexibility to fit intorelatively defined spaces. The actual processing of the rib graft wasdone aseptically and used no alcohols, peroxides or decontaminationsteps in its recovery. In doing so, the clinicians removed all of thecostal cartilage that they used for other applications and distribution.They cut the rib 100 at ends 15, 16 into relatively long segments atleast greater than 8 cm. Following that, they treated the graft for apredetermined time in 1N HCL (one normal hydrochloric acid) (20-50parts/gram) ranging from approximately 1-3 hours continuously inspectingthe graft rigidity. Once they were satisfied with the texture andflexibility of the graft 10 they washed it in a washing solution ofPhosphate buffered saline approximately 20 minutes. Then they cut therib 100 longitudinally to maintain its cylindrical configuration. Thiscut along the length allowed for either using the graft as a flat sheetconstruct or it could maintain the graft 10 in a cylinder. Thefenestration portion of the graft 10 is cut into the rib 100 and createdusing an in-house made bone cutter. Once the fenestrations or openings12 were made in the graft 10, the graft 10 was freeze dried using anovernight cycle and then packaged sterilely for clinical use in a peelpouch. Following the removal of the graft 10 from the plastic peel pouchit can be reconstituted in saline or lactated ringers with or withoutantibiotics for clinical applications. The graft 10 could be refoldedinto a cylindrical configuration and filled with either autologous orallogenic bone graft with or without stem cells moreover the graft 10could be rolled or folded into a confined space such as a cage or rolledinto a cylinder where it could be used for the application of satisfyinga short close open segment defect. The graft 10 could also be onlaidinto a vascularized myo-osseous pouch for the purpose of long segmentfusions in the spine, the thoracic or lumbosacral spine.

The tibial graft 20, as shown in FIG. 1, was conceived to create longersegments of bone for very long segment fusions in the case of scoliosisor a multi-segment instability or trauma of the spine. Again the graft20 was recovered from a tibia 200, in aseptic fashion without the use ofperoxides detergents or secondary decontamination steps. Secondarysterilization could however be employed if cultures were positive fornon-exclusionary organisms as outlined in FDA guidelines. Asepticcleaning in the processing state has been reinstituted and the tibiagraft 20 was cut on a band saw in a coronal fashion in lengths 10 cm orgreater, while the thickness is approximately 0.2 to 1 mm. To achieveeven thinner sheet material, the bone can be milled, planed or groundthinner 0.1 mm to 2 mm or preferably 0.05 to less than 1 mm so it couldbe used as a wrap or drape to be conformed onto solid 3-dimensionalstructures. The graft 20 was then placed in a large graft cylinder andtreated with 1N HCL (20-50 parts/gram) for 4-6 hours with continuousinspection to assess the rigidity and texture of the graft 20. Once theappropriate texture was obtained, it was then washed in phosphatebuffered saline three separate times for 20 minutes. The graft 20 wasthen placed on the bone cutter to create the appropriate fenestrationsor opening 12 bound by the interconnected bone struts 14 and then thetibia graft 20 was placed in the freeze drier for an overnight cycle. Itwas then packaged sterilely for clinical use. In using the tibia graft20, it was removed from the peel pouch and reconstituted in saline orlactated ringers with or without the addition of antibiotics and thendepending on the particular application, the tibia graft 20, like therib graft 10 would be onlaid or folded into a cylinder or a roll or abasket into which particulate graft could be added along with a stemcell. FIGS. 4 and 5 show a basket formed from fenestrated graft 10, 20strip folded over and laced or woven together to form the basket shape.So the indications for this graft 20 are felt to be long segment fusionsuch as scoliosis, multi-level and trauma as well as maxillofacialsurgery, surgery involving defects in cranial pulp, or long segmentdefects as well as any other defect.

FIG. 1 is essentially showing a portion of a 20 cm long fenestrated bonegraft 20 that was derived from the tibia 200. It is freeze dried andthis is done after the fenestrations 12 were created in the graft afterit was fully demineralized. Once this fenestrated bone graft 20 ishydrated it resumes its pliable shape and can be formed into severalalterations that can retain smaller bone particulate graft and stemcells.

FIG. 2 shows a cylindrical graft 10 made from rib 100. One notes thatthe fenestrations 12 are created by not having to longitudinally sectionthe rib 100, but using a more robust cut to create fenestrations 12throughout the graft 10. This is a very interesting graft because it canbe filled with allograft bone particulate graft or dbm or stem cells ora combination thereof and can be sewn or restricted above and below atends 15, 16 of the rib graft 10. This construct can be used to fill acage construct or potentially to augment a segmental defect or tosatisfy a defect in the portion of a long bone or a strip in a pelvis.

FIG. 3 is a higher power magnification showing the morphologic changesthat are created in the demineralized cortical bone followingfenestration. One notes the uniformity and openness of porous bonestructure and the intervening connective strut structure 14 of corticalbone.

The desired texture is a surface related property that has to do withthe pliability and stretchability of the grafts 10, 20 themselves. Ithas to be sufficiently demineralized to have the flexibility whichallows creating a variety of different shapes. If too stiff, obviouslyit can't create these shapes, if demineralized it too much it loses someof the inductivity that is inherent in demineralized bone. It istherefore considered preferable to mechanically reduce the bonethickness for the very thin bone wrap graft prior to demineralizing aspreviously discussed.

The cut openings 12 or fenestrations 12 are made with a punch press. Asshown, these openings 12 are oblong. One can make the openings 12 anysize desired. To entrap bone particles calls for pore sizes that aresmall. This will restrict micronized bone and one could see that theseare grafts 10 or 20 formed as strips having the actual pore size about 3mm long and 1.5 mm wide for the fenestrations 12. The bone connectionsor struts 14 or strut networks formed are about 1 mm or less indiameter, width or thickness 0.8 to 1.2 mm, at the connective portions,about double that. The actual sizes of the fenestrations 12 can vary ina range from fractions of a millimeter to several millimeters dependingon the graft application, 0.2 mm to 5 mm.

This bone graft 10 or 20 could be used as a spacer in the mid-foot andor the fore foot, because of its pliability.

With reference to FIG. 6, the allograft bone structure 10, 20 can bemade in the form of a pouch or pillow 10, 20. It uses 100% humandemineralized cortical sheet. The pillow 10, 20 is meshed, perforatedbone with fibrous cortical cancellous stuffing 300. The stuffing 300 canbe cancellous bone material, autologous or allogenic bone graft, with orwithout stem cells, allograft bone particulate graft or dbm or stemcells, BMA or any combination thereof. The pillow ends 15, 16 can besutured. Cortical sheet is machine stamped for consistency in the openarea as previously discussed. It has flexible handling characteristicswith osteoconductive and osteoinductive properties. It is easy to handleand deliver, is pre-configured implant sized to the specific procedureand it aims to solve the common problems of graft site migration and theability to visualize the implant post-surgery. It can be made availablein multiple lengths. It has a 5 year shelf life at room-temperaturestorage and can be conveniently distributed in packs of 2. As shown, thedemineralized cortical meshed perforated “pillows” 10, 20 can beprocessed from donated human bone utilizing the previously discusseddemineralization technology; the grafts are flexible and featureosteoinductive and osteoconductive properties. When combined with BMA,it provides all of the necessary elements for bone regeneration. It isdesigned for posterolateral and cervical spine surgery applicationsincluding single- and multi-level fusions, as well as deformityprocedures. It can be distributed in packs of 2 to provide fusionmaterial for both sides of the spine, thus minimizing the number ofboxes to open during procedures. It can be provided in various sizes,for example: 20 mm×50 mm (2) for Posterolateral applications; 10 mm×100mm (2) for Spinal Deformity; and 10 mm×50 mm (2) for Posterior Cervicalapplications.

With reference to FIGS. 7, 7A and 8, the present invention when madeinto a very thin sheet 402 can be made so flexible it can easily befolded like woven cloth mesh. The fenestration openings 12 and struts 14are shown magnified in FIG. 7A. When made very thin, the sheet 402 ofthe bone wrap graft 400 whether from a rib graft 10 tibia graft 20 orany other long bone like a femur.

As shown in FIG. 8, the fenestrated bone wrap graft 400 when made intothe very thin sheet 402 can be folded at the ends 404 along fold lines405. Ideally, the wrap 400 can be adhered when applied as a rehydratedor moistened sheet 402 to an implant device 500. As shown, the exemplaryimplant device is a spinal fusion implant 500 with an exterior surface502 having a bone growth enhancing pattern 504. As shown, the implant500 has a hollow cavity 510. The cavity 510 can be filled with cells orbone growth enhancing biological material then contained by the coveringprovided by the bone wrap graft 400. This insures the biologicalmaterial does not flow out of the device easily, but rather absorbs thepatient's blood flow through the fenestrations 12 to speed up the timerequired to create new bone.

Variations in the present invention are possible in light of thedescription of it provided herein. While certain representativeembodiments and details have been shown for the purpose of illustratingthe subject invention, it will be apparent to those skilled in this artthat various changes and modifications can be made therein withoutdeparting from the scope of the subject invention. It is, therefore, tobe understood that changes can be made in the particular embodimentsdescribed, which will be within the full intended scope of the inventionas defined by the following appended claims.

What is claimed is:
 1. A fenestrated bone wrap graft comprises: anallograft bone structure formed as a thin sheet having a thickness (t)of less than 1 mm, the allograft bone structure having an exterior orouter surface and an interior or inner surface, the structure beingfenestrated with a plurality of pores or openings extending through fromthe exterior or outer surface to the interior or inner surface to formopen passages; and wherein the material is conformable to wrap around asolid 3-dimensional surface.
 2. The fenestrated bone wrap graft of claim1 wherein the allograft bone structure is formed as a thin flat sheetconfigured to wrap or drape over solid objects or implants.
 3. Thefenestrated bone wrap graft of claim 1 wherein the allograft bonestructure is formed as a thin walled tubular or cylindrical shapedgraft, having a wall thickness of 1 mm or less.
 4. The fenestrated bonewrap graft of claim 1 wherein the allograft bone structure is madepliable.
 5. The fenestrated bone wrap graft of claim 4 wherein theallograft bone structure is conformable to flex about the surface of adamaged bone to provide a fenestrated bone wrap graft or to wrap about abone implant device to form a bone wrapped implant.
 6. The fenestratedbone wrap graft of claim 1 wherein the bone structure is from a rib. 7.The fenestrated bone wrap graft of claim 1 wherein the bone structure isfrom a tibia.
 8. The fenestrated bone wrap graft of claim 3 wherein thetubular or cylindrical shaped graft has a pair of ends that are foldableto close the ends of the graft.
 9. The fenestrated bone wrap graft ofclaim 8 wherein one of the ends is sutured closed to form a basket. 10.The fenestrated bone wrap graft of claim 9 wherein both of the ends aresutured or woven closed.
 11. The fenestrated bone wrap graft of claim 8wherein the basket is filled with one or more of cancellous bonematerial, autologous or allogenic bone graft, with or without stemcells, allograft bone particulate graft or dbm or stem cells, BMA or anycombination thereof.
 12. The fenestrated bone wrap graft of claim 9wherein the basket is filled with one or more of cancellous bonematerial, autologous or allogenic bone graft, with or without stemcells, allograft bone particulate graft or dbm or stem cells, BMA or anycombination thereof.
 13. The fenestrated bone wrap graft of claim 1wherein the bone allograft structure has a thickness of 0.1 mm to 1 mm.14. The fenestrated bone wrap graft of claim 13 wherein the openings aresized to be in the range of 0.2 mm to 0.5 mm.
 15. The fenestrated bonewrap graft of claim 14 wherein the structure form has struts in a sizeof 0.8 mm to 1.2 mm in length.
 16. The fenestrated bone wrap graft ofclaim 15 wherein at the connective portions of the strut the sizedoubles.
 17. The fenestrated bone wrap graft of claim 10 wherein whenboth ends are closed, the allograft bone structure forms a pouch. 18.The fenestrated bone wrap graft of claim 17 wherein the pouch is filledwith a stuffing made with one or more of cancellous bone material,autologous or allogenic bone graft, with or without stem cells,allograft bone particulate graft or dbm or stem cells, BMA or anycombination thereof.
 19. A method of creating a fenestrated bone wrapbone graft comprises the steps of: acquiring and cleaning a corticalbone; demineralizing the bone; removing the cancellous center; millingor planning the bone to form a thin sheet having a thickness of 0.1 toless than 1 treating the fenestrated bone in 1N HCL for a predeterminedtime to achieve flexibility; washing in washing solution; passing orotherwise cutting fenestrations into the bone; freeze drying; packingsterilely.
 20. The method of creating a fenestrated bone wrap bone graftof claim 19 further comprising folding the ends into a foldablewrapping.